Field of Invention
The invention relates to a reinforcing fibers for use in concrete. Particularly, the invention relates to improvements in concrete through use of the specific geometric reinforcing fiber.
Prior Art
There are various wire designs for mixing in concrete material. Such wire designs are for the reinforcement of synthetic resins, plastics, rubber and other materials, especially mortar and concrete, which only offer a small resistance to a tensile force. These typically employ pieces of wire, made of steel, glass fiber or another synthetic material of high tensile strength which, when mixed up in a material with enhanced strength.
In order to improve the strength characteristics for a given weight of wire material, it has been previously proposed to increase the concentration of wires in the mass by a greater subdivision of finer wires. Various length and diameter ratios have been tried to enhance grip of the wire on the material. In addition, corrugations, helicoidal or ring shaped wires have been tried to improve strength and hold.
The prior use of polymeric fibers (especially polypropylene) has to date remained limited to control of plastic shrinkage cracking in freshly placed concrete resulting from loss of mix and bleed water through evaporation. Given their non structural purpose, the volume fractions of fibers used in these applications have also remained low (approximately 0.1%). The load carrying capacity of plain concrete without fiber reinforcement or that of concrete carrying a minimal amount of polypropylene fiber reinforcement (approximately 0.1% by volume) beyond matrix cracking is essentially zero. There have been some attempts to introduce greater volume fractions (about 1%) of larger diameter polypropylene fiber into concrete. These fibers have brought polymeric materials into the category of “structural” fibers Where the purpose is not so much to control plastic shrinkage cracking, but also to improve the toughness, energy absorption capability and the load carrying capacity of concrete beyond first matrix cracking.
The prior “structural” polypropylene fibers develop a poor bond with the surrounding matrix and are not very efficient. What is not known to-date, however, is what constitutes an optimal deformation for a low modulus material as polypropylene. One attempt used a sinusoidally configured fibers for reinforcing concrete and like materials.
One of the complications in adding such wires is the inability to mix these in a manner which disperses them to a degree which meet the goals of enhanced strength. If the wires for fibers tend to cluster then there is created a weak spot in the resultant material. There is a continued need to find the best geometric solution and composition for enhancing the strength such materials.
The instant invention is believed to address the needs of finding and improved a geometric design for a fiber which also meets acceptable new mix-ability.